Radioactive ionizer for a combination changer



Aug. 1962 M. R. MORROW ET'AL 3,049,874

RADIOACTIVE IONIZEZR FOR A COMBINATION CHANGER Filed Oct. 0, 1958 FIG.2.

COMBUSTION CHAMBER FIG.

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United States Patent 3,049,874 RADIOACTIVE IGNIZER FQR A CGMBINATEONCHANGER Morris R. Morrow and Andrew D. Suttle, in, Baytown, Tex.,assignors, by meme assignments, to Esso Research and EngineeringCompany, Elizabeth, NJ, a corporation of Delaware Filed Oct. 30, 1958,Ser. No. 770,745 3 Claims. (Cl. 60-356) This invention relates to newand improved combustion engines. More particularly, this inventionrelates to a combustion engine having a combustion chamber constructedso as to provide for a more complete utilization of a volatilized fuel,a more efficient utilization of a volatilized fuel, or both.

In the generation of power by the combustion of a volatilized fuel, suchas a hydrocarbon, in the presence of a combustion agent such ashydrogen, air, etc., a severe limitation is imposed on the efficiency ofcombustion by the rate of production of the molecular fragments (e.g.,free-radicals) which are necessary for efiicient and rapid burning ofthe fuel.

In accordance with the present invention, there is provided a combustionengine constructed for the gas phase combustion of a fuel in acombustion chamber, such combustion chamber having a combustorcontaining a supported solid high specific activity film of a metallicradioactive material having a short-lived alpha active isotope orisotopic chain. For the purposes of this application, a short-livedalpha decay chain may be defined as a single alpha emission (singlestage) or a series of two or more (2 to alpha particles emitted with orwithout, but usually with, interspersed beta emission (plural stage).Thus, the alpha decay chain may have 1 to 10 stages. The intensity ofalpha emission should preferably be from about 10 to 10 alpha particlesper square cm. of film surface per second. The half-life should be lessthan 100 years and is preferably about 2 to 10 times the expected lifeof the engine, for reasons to be set forth hereafter.

Representative examples of suitable radioactive metallic alpha emitterswhich may be utilized in accordance with the present invention includepolonium lead radium, uranium etc.

It is a feature of the present invention that the alpha particle emitteris utilized in a combustor, the dimensions of which are not greater thanabout 4 times the range associated with the average energy of alphadecay.

- As an indication of the range associated with various alpha energies,we cite the following table.

TABLE I Travel Distances, R, in Various Media Particle energy E (mev.):oar (cm. air) 0.5 0.385

ice

combustion engines such as reciprocating combustion engines, dieselengines, jet turbine engines, oombustors for gas turbines, etc.

In accordance with the present invention, the alpha source is positionedin the combustor (i.e., oxidation chamber). The ionization density ofalpha particles is much greater than that of beta or gamma radiationsand therefore its energy is dissipated over much smaller paths. Therange of all alpha particles is less than 1 cm. of aluminum and,therefore, the need for shielding is greatly minimized. In the normalengine, alpha energy is completely attenuated in the engine. Thus,shielding is normally required only when decay chains are employed whichalso emit beta or gamma radiation, or both. The low energyelectromagnetic radiation associated with alpha decay will also beefliciently absorbed in materials commonly used in engine construction.

Accordingly, in accordance with one form of the present invention, analpha emitter which substantially eX- clusively emits alpha particlesonly is positioned in a manner to be described in an unshieldedcombustor. In accordance with another form of the present inventionwherein beta or gamma radiation, or both, is present also, the emitteris utilized in an engine shielded in a manner to minimizebiora-diological effects. Representative examples of emitters of bothclasses are given in the following table.

TABLE II Bi by the reaction Bi (n, Bi Po the decay of U and/or Ra Ra"produced from Ra by the reaction Ra (12, 'y) Ha Mic Po produced from Pbrecovered from U produced from Pa by the reaction Pa (n, 7) Pa U 1Includes a portion of the B- and decay energy.

In general, in situations wherein the internal combus tion engine isutilized as a source of energy for propulsion (e.g., automobiles, etc.)it will generally be preferable to utilize pure alpha emitters such asP0 and Pb in order to minimize and reduce problems associated withshielding. However, in large stationary installations whereinmaintenance can be elfected by remote control or where massive shieldingis feasible, it is desired to utilize decay chains such as Ra or Ubecause of the potentially larger amount of recoverable energy containedin such chains.

In situations wherein the alpha emitter is emitted as a part of a decaychain, it is desirable that the alpha emitter be present in a stable,dense film in order that the emitting isotopes may be retained in thefilm. This is desirable in order to prevent contamination of the exhaustsystem and in order to utilize the energy recoverable from the decayproducts.

The invention will be further illustrated by the accompanying drawingswherein:

FIG. 1 is a schematic elevational side view, partially 35 in section, ofa cylinder of an internal combustion engine;

FIG. 2 is a schematic elevational side view, partially in section, of adiesel engine;

FIG. 3 is a schematic elevational view, tion, of a jet engine; and

FIG. 4 is a schematic elevational view, in section, of a combustor for aturbine, such combustor having associated therewith suitable means forpositively regulating alpha emission.

Turning now to FIG. 1, there is provided a cylinder closed with a head14 of conventional construction and having housed therein areciprocating piston '12. The head 14 is provided with suitable ignitionmeans such as a spark plug 16, an inlet valve 18 and an exhaust valve20. In accordance with the present invention, a film of a material whichpreferably emits alpha radiation only is deposited on the inner surface22 of the cylinder or the face 24 of the piston, or both. Normally, onlythe face 24 of the piston or the wall 22 of the cylinder will besurfaced. When the interior wall 22 of the cylinder is to be surfacedwith an alpha emitter, the surfacing is applied only to that portion ofthe cylinder lying above the maximum stroke of the piston.

By way of specific example, a thin layer of a supporting metallicsubstrate such as copper, silver, gold, platinum, or rhodium isdeposited on the face 24 of the piston 12. Onto this substrate there isdeposited a very thin layer of free Po having a thickness not in excessof 10 micrograms per square cm. Both the substrate and the alpha emittermay be applied to the piston face in any suitable manner such as by wayof electric deposition, sputtering, evaporation, or the ignition ofreadily reduced compounds or mixtures of such compounds.

In situations wherein the substrate is a catalyst for the combustionprocess as is the case with platinum, still greater efliciency ofcombustion is obtainable.

In the operation of a reciprocating piston-type internal combustionengine chamber of the type illustrated in FIG. 1, the combustionsequence is that which is normally associated with the operation ofengines of this type. Thus, the fuel inlet valve 18 is opened on thedownstroke of the piston to permit the introduction of a mixture of airand vaporized gasoline. The valve 18 closes and the mixture iscompressed on the next upstroke of the piston 12. At the height of thestroke, a spark is generated by the plug 16 whereby ignition of thegasoline vapors is initiated. In contrast, with a conventionalcombustion procpartially in secess, however, the following sequence ofevents will occur.

The ionizing radiation will have, previous to the spark, created asteady state concentration of radicals which will be present in acatalytically effective amount. That is to say, the free radicals in theunburned portion of the compressed mixture will have an excitationsufficient to permit an appreciably faster rate of travel of the flamefront (i.e., an increase within the range of about 2 to 100 times). As aconsequence, the accelerated flame front will develop a higher absolutetemperature and move at a greater speed whereby the force exerted on theface 24 of the piston 12 will be increased. The expansion of thecombustion products will force the piston 12 downwardly for the powergenerating stroke. Thereafter, on the next succeeding upstroke of thepiston 12 the exhaust valve 20 is opened to remove combustion productsfrom the interior of the cylinder 10.

The operation of the diesel-type piston shown in FIG. 2 is substantiallysimilar. In this case, however, a heavier fuel such as Diesel oil isutilized and ignition is accomplished by more severe compression of themixture of fuel and oxygen.

Thus, in the case of a combustor for a diesel-type engine, there isprovided a cylinder 50 closed with a head 52 of any suitableconventional construction. The head 52 is provided with a fuel combustor54, an inlet valve 56, and an outlet valve 58. A piston 60 is mountedwithin the cylinder 10.

In addition, a material which preferably emits only alpha radiation isdeposited as a film 62 on the face of the piston 60. Optionally, thefilm may also be present on the iner surface of the cylinder as a film64 positioned above the maximum stroke of the piston 60.

In operation, on the downstroke of the piston 60 the inlet valve 56 isopened to admit air and, at the same time, fuel is injected into thecylinder through the line 54. The valve 56 is then closed and on theupstroke of the piston 60 the mixture of gas and fuel is compressed toan extent suflicient to cause combustion. In this instance, however, thepresence of the alpha emitter will promote the combustion process toprovide for a more efficient utilization of the fuel.

After the power-generating downstroke, the piston 60 again returnsupwardly and the outlet valve 58 is opened to remove combustion productsfrom the chamber of the cylinder 50. The cycle then repeats.

Advantages are obtainable with disel-type pistons to a greater degreethan with internal combustion engines due to the nature of the fiameignition process. Thus, with a diesel engine, the presence of ionizedfuel particles which will exist homogeneously throughout the compressedmixture of vaporized diesel fuel and oxygen makes possible ignition ofthe system at either a lesser pressure or the generation of greaterpower for the same pressure.

Another form of the present invention is shown in FIG. 3 wherein thereis schematically shown a jet engine comprising a housing defining an airintake 102 leading to a centrifugal compressor 104 communicating with acombustion chamber 106. A suitable jet fuel is fed to the combustionchamber 106 through fuel injection nozzles 108-110 to provide forcombustion of the fuel in the presence of compressed air. Hot exhaustgases pass through a rotor 112 for operation of the compressor 104 andfrom thence through an exhaust duct 114 in order to generate the desiredthrust.

In accordance with the present invention, a screen 116 comprising aradioactive material which substantially exclusively emits alphaparticles is mounted in the combustion chamber 100. The screen 116 may'be composed of a substrate formed of suitable metal such as platinum orrhodium, the wire of the screen having a diameter of 0.5 mm. or less,and a mesh of 5 to 10 mm. There is deposited on the wire substrate analpha emitting isotope such as Pb It is desirable that about 0.03 toabout 1.0 kilocurie of the isotope be deposited uniformly on the screenin the form of a thin coating. Techniques mentioned above with respectto FIG. 1 may be utilized for this purpose. The screen is preferablycylindrical in shape, of a diameter approximating about onehalf thediameter of the combustion chamber and a length substantially equal tothe length of the combustion chamber.

In FIG. 4 there is shown, schematically, improved means for driving aturbine for the generation of power. Thus, there is schematically showna turbine 200* to which hot gas is charged from a combustion chamber 202and from which spent gas is discharged by way of an exhaust 204. Aninlet line 206 is provided for introducing either air or a fuel into thecombustion zone 202 and a separate inlet line 208 is provided forintroducing the other element necessary for combustion into thecombustion chamber. Mounted within at least one of the inlet lines, suchas the inlet line 208, is a screen 210 composed of platinum or rhodiumor other refractory metal having a thin film of U having a thickness ofthe order of about 1 to 100 micrograms per square centimeter. The screen210 is movably mounted on a shaft 212 whereby a desired selected portionof the screen 210 may be physically introduced into the combustionchamber 202.

In operation, asuitable fuel such as natural gas may 202 under controlof the unit 224.

be introduced by way of the line 206. Air is introduced into the inletline 208 by way of a branch line 214, passes over the enclosed portionof screen 210 and from thence into the combustion chamber 202. Anyionized entities formed within the inlet line 208 will havesubstantially decayed prior to entry into the combustion chamber 202whereby the eifective ionization will occur substantially exclusively inthe chamber 202. The combustion process is assisted in the aboveescribedmanner whereby the natural gas is heated to a higher temperature in thechamber 202 than would normally be obtainable. Stated differently, agreater volume of gas is burned per unit volume of com-bustion chamberper unit of time. It will be understood that in this situation it willbe necessary to shield at least the inlet line 208 and the chamber 202with a suitabfle material such as concrete, high density tungstenalloys, etc. if ,8 and 7 emitters are used.

A problem is encountered with an installation of this nature withrespect to proper control of the process. In accordance with theembodiment of the invention shown in FIG. 4, suitable means are providedfor controlling the intensity of radiation within the combustion chamber202 in response to the combustion process and for causing any failure ofthe system to be a fail safe failure.

Thus, by way of specific example of a control system of this nature, theshaft 212for the screen 210 is actuated by a prime mover such as a motor216 which, in turn, is regulated by a suitable control mechanism such asa slave Selsyn 218.

The slave Selsyn 218 may, in turn, be actuated in response to a processvariable The position of the screen 210 is thus made dependent uponselected variables of the engine or turbine such as the rate of flow offuel and/ or the temperature at various positions in the system. Thus,in operation of the turbine or engine, the flow of either component maybe used to rotate a small aerometer or rotameter 220 Which, in turn,actuates an alternator 22 whose frequency or potential is a proportionalfunction of the gas flow. The signal generated in this alternator isamplified (and shaped, if desired) by a control unit 224. An outputsignal from the unit 224 may be fed to a master Selsyn 226 in order tocontrol the motor 216 which guides the screen 210 into or out of thecombustion Zone 202. In this way, it is possible to control the reactionrate and maintain optimum conditions. Should it also be desirable not toexceed a preselected temperature, a temperature sensing device such as athermocouple 228 may be positioned ata critical location in the deviceand used as a source for an override control.

Thus, a signal may be transmitted from the thermocouple 228 through aline 2.30 to a control unit 232 which may be, for example, a signalamplifier and shaper. One output signal from the control unit 232 maypass to a second master Selsyn 234 electrically coupled with the slaveSelsyn 218 and the initial master Selsyn 226 in the manner shown in FIG.4. The second signal from the control unit 232 may pass to an overridecontrol unit 236 designed to nullify the signal from master Selsyn 226when the temperature is excessive. Thus, the override signal willcontrol the motor for the screen 208 in response to a signal from thecontrol unit 232.

Accordingly, if the temperature at any point exceeds a selected value,the source 298 will be withdrawn and the combustion rate decreased untilthe temperature has fallen to the desired value, at which time theoverride 236 is cut out. The source 2% is advanced into the chamber Inthis way, a fail safe control is maintained regardless of the selectedoperating conditions.

Special attention should be directed to selecting radionuclides whichhave high specific power. For example, 1 gram of carrier-free P releasesabout 24 cal. sec? or 100 joules per second (i.e., 100 Watts) and theother activities mentioned produce similar powers. This is to becontrasted with the specific power of U thorium or even Ra which releaseless than one-thousandth the amount of energy cited here. This isdesirable, if not absolutely essential, because the range of the alphaparticle being short precludes the use of thick deposits. Motors whichare subject to frequent maintenance will naturally employ the pure alphadecay isotopes of short half-life (e.g., P0 while those which willoperate for extended periods of time without attention will be sustainedby the longer-lived decay chains.

In the applications under consideration, alpha activities are preferredto other emissions. The range of alpha particles is short and they arestopped entirely in the gases being burned while the beta particles orgamma rays will only partially be attenuated under these conditions.Furthermore, the energies of alpha decay generally exceed 5 mev. whilean energetic beta of useful or suitable half-life seldom has more than 3mev. maximum energy and in unforbidden beta decay two-thirds of theenergy is carried oif by neutrons which have extremely small absorptioncross-sections.

Having thus described our'invention, what is claimed is:

1. In a device for generation of power by the burning of a volatilizedfuel with a volatilized combustion agent in a combustion zone to providehot combustion gases for the actuation of a turbine fed with hot gasesfrom said combustion zone, said combustion zone being provided withseparate conduits for the introduction of said fuel and said combustionagent, the improvement which comprises, in the combustion zone, ametallic screen, a high surface area deposit of a metallic radioactivematerial emitting principally alpha particles, having an intensity ofalpha emission within the range of about 10 to about 10 alpha particlesper square centimeter of film surface per second and having an alphadecay chain with about 1 to 10 stages, said screen being reciprocablymounted within one of said inlets, and. control means for reciprocatingthe mounting for said screen whereby a selected desired portion of saidscreen may be withdrawn from said combustion zone.

2. In a device for the generation of power by the burning of avolatilized fuel with a volatilized combustion agent in a combustionzone to provide hot combustion gases for the actuation of a turbine fedwith hot gases from said combustion zone, said combustion zone beingprovided with separate conduits for the introduction of said fuel andsaid combustion agent, the improvement which comprises, in thecombustion zone, a metallic screencomposed of a metal of the groupconsisting of platinum and rhodium, the Wire of said screen having adiameter of not more than about 5 mm. and the mesh of said screen beingnot more than about 10 mm. and, deposited on said Wire, a metallic alphaemitter selected from the class consisting of lead and polonium in anamount suificient to provide a deposit having an intensity within therange of about 0 .03 to about 1.0 kilocurie of alpha emitter, saidscreen being reciprocably mounted Within one of said inlets, and controlmeans for reciprocating the mounting for said screen whereby a selecteddesired portion of said screen may be withdrawn from said combustionzone.

3. A device as in claim 2 including operating means for regulating saidcontrol means, said operating means comprising first electricaldetecting means for measuring a combustion variable, first electricaloutput means coupling said first detecting means with said control meansfor regulation of said control means in response to said measurement ofsaid combustion variable, second electrical detecting means formeasuring the temperature of the combustion products at a preselectedcritical point,

second electrical output control means electrically coupling said seconddetecting means with said control means and an override electricallycoupling said first output means with said second output means foroverriding said first output means in response to measurement of a pre-8 selected temperature by said second electrical detecting 2,791,883Moore et a1. May 14, 1957 means. 2,350,641 Martin Sept. 2, 1958References Cited in the file of this patent FOREIGN PATENTS T T 782,908France Mar. 25, 1935 1777 554 E SiATES PALEMSO t 7 1930 5 792,776 France061. 28, 1935 no 01111 c. 1,820,878 WyckofE Aug. 25, 1931 OTHERREFERnNCES 2,721,788 Schad Oct. 25, 1955 Production of Unipolar Air WithRedium Isotopes, 2,723,349 Rylsky Nov. 8, 1955 reprint from ElectricalEngineering, January 1954.

2,766,582 Smith Oct. 16, 1956 10 published by the A.I.E.E,

